Various stabilizers are known for the conventional polyurethanes based on polyether polyols or hydroxy-terminated polyesters. These stabilizers, however, are not adequate for a newly developed class of polyurethane polymers obtained by the reaction of polyisocyanates with functionally terminated butadiene polymers, or for the class of polymers obtained by curing a carboxy-terminated butadiene polymer with an aziridine or epoxide. The unique stabilization problems associated with these polymers are believed to be due to the presence of both olefinic unsaturation and urethane or other hetero atom linkages in the polymer chain. The present invention is believed to represent a significant advance in the art by providing a combination of stabilizers for this class of polymers which is uniquely effective in stabilizing the polymer against degradation due to oxidation and decomposition of the urethane or other hetero linkages.